Burglar-alarm system



(No Model.) A. STROMBERG.

- BURGLAR ALARM SYSTEM.v No. 530,976.

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NITED STATES PATENT OFFICE.

ALFRED STROMBERG, OF CHICAGO, ILLINOIS.

BU RG LAR-AL'ARM SYSTEM.

SPECIFICATION forming part of Letters Patent No. 530,976, dated December 18, 1894.

To all whom may concern.-

I (Case No. of which the following is a full,

clear, concise, and exact description, reference.

being had to the accompanying drawings, forming a part of this specification.

My invention relates to burglar alarm systems, and its object is the provision of means for the protection of windows, doors, and other openings, and, further, to provide means for readily testing the protective circuits to determine the presence and the location of faults in the system.

My invention, in its preferred embodiment, comprises a plug, provided with contact terminals, adapted to be inserted into a socket to complete'an electric circuit and establish upon the protective circuits a normal condition, which, if disturbed by the withdrawal of the plug, or in other manner,

will result in the transmission of a signal to the central station to sound an alarm. The

plug and socket are so associated with the movable portion of the opening that the plug must be removed from the socket in order that the opening may be uncovered.

I will describe my invention by reference to the accompanying drawings, in which Figure 1 is a diagrammatic view of a system embodying my invention. Fig. 2 is a View of a window provided with a plug and socket after the manner of my invention. Fig. 3is a view of the plug inserted in the socket, the latter being shown in section. Fig. 4 is a longitudinal sectional view of the plug. Fig. 5 is a similar View on a plane at right angles to said view. Fig. 6 is an end View of the plug and socket looking from the rear of the socket. Fig. 7 is a front view of the socket.

Like letters refer to like parts in the several figures.

The socket comprises a plate or adapted to be screwed against the window sash, a recess being provided behind'the plate for the reception of the springs a a which are secured Application filed May 24, 1894.. Serial No. 512,340- (No model.)

to the back of the plate. The plug b comprises a shell I) from the end of which extend three relatively insulated plates 1) 1) b the middle plate, 6 being connected to ground, while the other two plates are connected respectively to the opposite sides of the circuit. The middle plate I) is of a greater width than the outer plates so that in testing, circuit may be closed between the inner and an outer plate as will be hereinafter described. Whenthe plug is inserted in the socket, the plates b and b make-contact respectively with the springs a and a said springs being electrically connected, circuit being thus completed between. the plates. The inner plate 19 remains insulated from the springs and the outer plates.

The plug 1) is mounted upon the end of a cord 0, Fig. 2, from which it may depend during the day, or such other time as the protective circuit may not be in operative condition.

The plate a is located upon the upper sash and at such a distance from the lower sash that the latter cannot be raised without the removal of the plug.

In Fig. 1 a. number of plugs, as above described, are illustrated diagrammatically as placed in the sockets at the several openings to. be protected, circuit being closed through the outer plates 11 b at-the several plugs. The plugs are thus connected-in series,'an'd the removal of any plug will serve to open the circuit and sound the alarm at the central station. The central station apparatus, comprises a battery d and signal device d in a normally open local circuit. An electromagnet d is energized by the normally flowing current to attract its armature, the armature being released to close the local circuit when the current ceases to flow. A second electro-magnet d is adapted to attract its are mature when an abnormally large current At night the contact arm f rests upon the terminal N, thus completing the circuit between the protected district and the central ottice. During the day the arm f rests upon termi- IOO nal D so that it may be determined if at any time during the day the line be out between the central ofiice and the protected district.

To test the protective circuits to determine the presence of and to locate faults, a testing set, comprising a battery h, bell h and key 71 is connected between terminal N and ground. The circuit through the plugs is arranged in sections so that one section at a time may be tested. Thus if the windows of a building be protected, the windows upon theseveral floors may be included in as many separate sections. A key is is provided at the end of the first section which normally rests against anvil to complete the circuit, but which, when depressed, is adapted to make contact with the grounded anvil k Likewise, a key Z and contact anvils Z Z are provided at the end of the second section, and so on. The switch key 77.2 being closed, the key it is depressed, thus. closing the battery It and bell h in circuit with the first section of the protective circuit. If the protective circuit be complete, the bell will ring, as the current from the battery will find circuit therethrough. If the bell does not ring, it will indicate that the line is open in the first section. Suppose the line be open at 6. Connection is first made at the first plug between the inner plate b and the plate 5 the circuit of the battery and bell being thus completed through the ground branch connected to the several inner plates b will indicate that the fault does not exist between the first plug and the terminal N. Test is next made at the second plug, in a similar manner, and the ringing of the bell indicates that the circuit is in proper condition between the second plug and the first. When, however, test is made at the third plug, between which and the second plug exists the open circuit at t', no current will flow and the bell will not ring, thus locating the fault between the second and the third plug. The fault having been corrected and the first section testing out all right, test is made upon the second section, first by depressing the key Z at the end of said section, thus throwing the first and second sections in circuit with the battery and bell. If the bell ring, it will indicate that the second section is in proper condition. If not, test must be made at each plug, beginning with the first plug of the section, until the fault is found, after which the next section may be tested, and B0 on.

The resistance e is located beyond the last plug of the system, so that should an attempt be made to ground the line at any point, said If the bell rings, it

resistance will be cut out, and the increased current flow will actuate magnet 61 to close the local circuit and sound the alarm.

It will appear that my invention is susceptible of modifications, and I do not, therefore, desire to be confined to precise details, but,

Having described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. The combination with a removable covering for an opening, of a socket provided with contacts, a removable plug provided with contacts adapted when the plug is inserted in the socket to engage the contacts of said socket to complete a protective circuit, said socket being so located that the plug, when inserted therein, will lie in the path of saidremovable covering to prevent the uncovering of the opening without the removal of the plug, and signal apparatus in circuit with said plug adapted to sound an alarm when the plug is withdrawn from the socket, substantially as described.

2. The combination with a series of openings to be protected, of a series of plugs and sockets associated therewith, said plugs being provided with terminals adapted to be closed together to complete an electric circuit when the plug is inserted in the socket, said plugs being each provided with a normally insulated grounded terminal; whereby tests may be made, substantially as described.

3. The combination with a protective circuit, of a series of plugs and sockets through which said circuit is normally completed, said plugs being each provided with a grounded,

normally insulated terminal, and a testing battery and signal device adapted to be connected in circuit to determine the presence and location of faults on the circuit, substansignal device adapted to be connected with it the circuit to determine the presence and location of a fault on the line, substantially as described.

In witness whereof I hereunto subscribe my name this 11th day of May, A. D. 1894.

ALFRED STROMBERG.

Witnesses:

W. CLYDE J ONES, GEORGE L. CRAGG.

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